The present invention relates to fabric softener compositions adapted for the use in the rinse cycle of a laundering process and in particular to concentrated aqueous fabric softener compositions which are stable at both low and high ambient temperatures, i.e. such compositions do not form a gel, and which are easily dispersed in water when used.
Compositions containing quaternary ammonium salts having at least one long chain hydrocarbyl group are commonly used to provide fabric softening benefits when employed in a laundry rinse operation; for example, see U.S. Pat. Nos. 3,349,033; 3,644,203; 3,946,115; 3,997,453; 4,073,735 and 4,119,545.
For most aqueous softener compositions containing cationic quaternary ammonium compounds as active ingredients, the concentration of such cationics has, in general, been limited to the range of about 3 to 6% by weight (see U.S. Pat. Nos. 3,904,533 and 3,920,565). Such a low concentration is generally necessitated by the fact that cationics form gels in water systems at concentrations at above about 8%, and while the use of electrolytes to lower the viscosity of such compositions is know (see in particular U.S. Pat. No. 4,199,545), such electrolytes are far from satisfactory. From a functional point of view, the electrolytes often do not perform as required particularly at concentrations of the cationics in the neighborhood of about 12-15%. Further, while the performance of the electrolytes may mitigate some of the gelling problem, their use is far from satisfactory in providing a highly concentrated aqueous system of cationics which does not gel or severely change in viscosity within the usual range of temperatures encountered in the handling thereof, for example 0.degree. F. (about -18.degree. C.) up to about 140.degree. F. (about 60.degree. C.). In U.S. Pat. No. 3,681,241 a concentrated fabric softening emulsion is described which consists essentially of 3.5 to 6.5 parts by weight of a compound represented, for example, by distearyl dimethyl ammonium chloride, from 3.5 to 6.5 parts by weight of an alkyl amido imidazolinium alkylsulfate, and from 0 to 3 parts by weight of a different but similar fatty amido imidazolinium alkylsulfate, the latter allegedly providing low temperature stability for the composition. The total actives contemplated range from about 8 to 13%.
In British application 2053249A published Feb. 4, 1981, there are disclosed cationic fabric softening compositions containing 15 to 60% by weight of cationic softener, 25 to 75% by weight of an aqueous medium, and 0.5 to 40% by weight of a specified water soluble polymer.
In U.S. Pat. No. 3,974,076 there are disclosed quaternary ammonium-containing softening composition of conventional cationic concentrations, i.e. about 3% to about 6%. These compositions are characterized by the very small particle size of the substantially water-insoluble quaternary ammonium softening compound, i.e. 90% by weight of the quaternary ammonium compounds exist as particles which will pass through a 1.2 micron filter. The compositions are described as a combination of the cationic softener, a C.sub.8 to C.sub.20 alkyl alcohol with from about 0.1% to about 2.0% of a non-ionic surfactant having a HLB of from about 8 to about 15, and preferably from about 10 to about 14. The preferred non-ionics have a lipophilic hydrocarbyl moiety equivalent of 9 to 15 carbon atoms with 7 to 13 ethylene oxide hydrophilic moieties. This patent does not relate to the problem of stability of concentrated aqueous cationic softening compositions but rather to improving the level and uniformity of softening using conventional concentrations.
Each of U.S. Pat. Nos. 4,076,632; 4,157,307 and 4,233,164 discloses quaternary ammonium softening containing inter olia, "protonated" ethoxylated amine, but none of these disclose salts of the amine, let alone with high molecular weight organic acids (i.e. higher fatty acids e.g. C.sub.12 to C.sub.30 ; alkyl aryl sulfonic acids e.g. C.sub.12 to C.sub.18 alkyl benzene sulfonic acids; C.sub.12 to C.sub.30 paraffin (alkyl) sulfonic acids; C.sub.12 to C.sub.30 olefin sulfonic acids; the mono- & di-phosphoric acid esters of C.sub.8 to C.sub.30 alcohols including the ethoxylates of such alcohols with from one to 100 moles of ethylene oxide). U.S. Pat. No. 4,118,327 describes conventional cationic concentration (0.1 to 10% preferably 1 to 8% by weight) with phosphate organoesters as anti-static agents.